Light emitting device, method of manufacturing light emitting device, and lighting tool for vehicle

ABSTRACT

A light emitting device, according to the present embodiment, has a light emitting panel, a flexible wiring substrate, a mold resin and a protective tape. The light emitting panel has a first substrate, which is transparent to light, a plurality of conductor patterns, which are formed on a surface of the first substrate, a plurality of light emitting elements, which are connected to any of the conductor patterns, and a resin layer, which holds the light emitting elements on the first substrate. The flexible wiring substrate has a circuit pattern that is electrically connected with an exposed part of the conductor patterns. The mold resin covers the exposed part of the conductor patterns and an exposed part of the circuit pattern. The protective tape covers the mold resin, and is wound around a joint part of the light emitting panel and the flexible wiring substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 16/713,256, filedDec. 13, 2019, which claims the benefit of priority from Japanese PatentApplication No. 2018-235711, filed Dec. 17, 2018, and Japanese PatentApplication No. 2019-150652, filed on Aug. 20, 2019; the entireties ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

Embodiments of the present invention relate to a light emitting device,a method of manufacturing a light emitting device, and a lighting toolfor vehicles.

BACKGROUND OF THE INVENTION

A light emitting device that is flexible and that has a light emittingpart and external wiring to be connected to the light emitting part, hasbeen disclosed.

The light emitting part of the light emitting device has a pair ofinsulated substrates that are translucent and flexible, a plurality oflight emitting elements that are arrayed between the pair of insulatedsubstrates, an internal wiring pattern that is formed on an innersurface of at least one of the pair of insulated substrates, and that isconnected to the light emitting elements, and a resin layer that isprovided between the pair of insulated substrates, and that istranslucent and insulated. Also, an end part of the external wiring isbranched into a plurality of wirings having a line width narrower thanthe line width of the internal wiring. Furthermore, an end part of theinternal wiring pattern is joined to the end part of the externalwiring, which is branched into a plurality of wirings, by using ananisotropic conductive adhesive, at an end part of the insulatedsubstrates.

The light emitting device described above has problems, such asdielectric breakdown being produced in the joint part of the lightemitting part and the external wiring due to migration, highsusceptibility to deterioration over time, and so on.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a light emitting device according to afirst embodiment;

FIG. 2 is an exploded perspective view of the light emitting device;

FIG. 3 is a side view of a light emitting panel;

FIG. 4 is a plan view of the light emitting device;

FIG. 5 is a perspective view of a light emitting element;

FIG. 6 is a diagram showing the light emitting element connected to amesh pattern;

FIG. 7 is a side view of a flexible cable;

FIG. 8 is a diagram showing a joint part of the light emitting panel andthe flexible cable;

FIG. 9 is a diagram for illustrating a method of manufacturing the lightemitting device;

FIG. 10 is a diagram for illustrating the method of manufacturing thelight emitting device;

FIG. 11 is a diagram for illustrating the method of manufacturing thelight emitting device;

FIG. 12 is a diagram for illustrating positional relationships between aresin layer and substrates;

FIG. 13 is a diagram for illustrating positional relationships betweenthe resin layer and the substrates;

FIG. 14 is a diagram showing a table that shows test results of samples;

FIG. 15 is a diagram for illustrating a light emitting device accordingto a variation;

FIG. 16 is a diagram for illustrating a method of manufacturing thelight emitting device according to the variation;

FIG. 17 is a perspective view of a light emitting device according to asecond embodiment;

FIG. 18 is an exploded perspective view of the light emitting device;

FIG. 19 is a plan view of the light emitting device;

FIG. 20 is a diagram showing a joint part of a light emitting panel anda flexible wiring substrate;

FIG. 21 is a diagram for illustrating a method of manufacturing thelight emitting device;

FIG. 22 is a diagram for illustrating the method of manufacturing thelight emitting device;

FIG. 23 is a perspective view of a composite sealing material;

FIG. 24 is a diagram for illustrating the method of manufacturing thelight emitting device;

FIG. 25 is a diagram for illustrating the method of manufacturing thelight emitting device;

FIG. 26 is a diagram for illustrating the method of manufacturing thelight emitting device;

FIG. 27 is a diagram showing results of a cross-sectional voidobservation test and an infiltration search test;

FIG. 28 is a diagram for illustrating a summary of a 90-degree peelingdurability test;

FIG. 29 is a diagram showing a result of the 90-degree peelingdurability test;

FIG. 30 is a diagram for illustrating a summary of a 90-degree peelingdurability test;

FIG. 31 is a diagram for illustrating a summary of the 90-degree peelingdurability test;

FIG. 32 is a diagram showing a result of the 90-degree peelingdurability test;

FIG. 33 is a diagram showing evaluation results of a Joint-PartTensile-Reliability test;

FIG. 34 is a diagram showing evaluation results of the joint-partrepeated bending reliability test;

FIG. 35 is a diagram for illustrating a shape of a light emitting panel;

FIG. 36 is a diagram showing a variation of the light emitting panel;

FIG. 37 is a diagram showing a variation of the light emitting panel;

FIG. 38 is a diagram showing a manner of use of a light emitting device;

FIG. 39 is a diagram showing a manner of use of a light emitting device;

FIG. 40 is a diagram showing a variation of a light emitting panel;

FIG. 41 is a photograph showing a cross-section of a joint-part of alight emitting panel and a flexible wiring substrate; and

FIG. 42 is a photograph showing a cross-section of the joint-part of thelight emitting panel and the flexible wiring substrate.

DETAILED DESCRIPTION OF THE INVENTION

The light emitting device according to the present embodiment has alight emitting panel, a flexible wiring substrate, a mold resin, and aprotective tape. The light emitting panel has a first substrate that istransparent to light, a plurality of conductor patterns that are formedon a surface of the first substrate, a plurality of light emittingelements that are connected to any of the plurality of conductorpatterns, and a resin layer that holds the light emitting elements onthe first substrate. The flexible wiring substrate has a circuit patternthat is electrically connected to an exposed part of the conductorpatterns, exposing from an end part of the resin layer. The mold resincovers the exposed part of the conductor patterns and the exposed partof the circuit pattern, and also covers an end part of the lightemitting panel and an end part of the flexible wiring substrate. Theprotective tape covers the mold resin, and is wound around the jointpart of the light emitting panel and the flexible wiring substrate.

First Embodiment

Now, a first embodiment of the present invention will be described belowwith reference to the accompanying drawings. The following descriptionwill use an XYZ coordinate system, consisting of an X axis, a Y axis anda Z axis that are orthogonal to each other.

FIG. 1 is a perspective view of a light emitting device 10 according tothe present embodiment. Also, FIG. 2 is an exploded perspective view ofthe light emitting device 10. As can be seen by referring to FIG. 1 andFIG. 2 , the light emitting device 10 has a light emitting panel 20, aflexible wiring substrate 40 that is connected to the light emittingpanel 20, and a connector 50 that is mounted on the flexible wiringsubstrate 40. A protective tape 60 is bonded to the joint part of thelight emitting panel 20 and the flexible wiring substrate 40.

FIG. 3 is a side view of the light emitting panel 20. As shown in FIG. 3, the light emitting panel 20 has a pair of substrates 21 and 22, aresin layer 24 that is formed between the substrates 21 and 22, andeight light emitting elements 30 ₁ to 30 ₈ that are arranged inside theresin layer 24.

The substrates 21 and 22 are rectangular substrates, whose longitudinaldirection runs along the X-axis direction. The substrate 21 is afilm-like member that is approximately 50 to 300-μm thick. Thesubstrates 21 and 22 are transparent to visible light. The totalluminous transmittance of the substrates 21 and 22 is preferably about 5to 95%. Note that the total luminous transmittance refers to the totalluminous transmittance measured in conformity with the JapaneseIndustrial Standard JISK7375: 2008.

Also, the substrates 21 and 22 are flexible, and their bending modulusof elasticity is 0 to 320 kgf/mm², approximately. Note that the bendingmodulus of elasticity is a value that is measured by a method inconformity with ISO178 (JIS K7171: 2008).

As for the materials for the substrates 21 and 22, polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC),polyethylene succinate (PES), arton (ARTON), acrylic resin and so forthmay be used.

A conductor layer 23, approximately 0.05 μm to 2-μm thick, is formed inthe lower surface of the substrate 21 (the surface on the −Z side inFIG. 3 ) between the pair of substrates 21 and 22.

FIG. 4 is a plan view of the light emitting device 10. As can be seen byreferring to FIG. 4 , the conductor layer 23 is comprised of an L-shapedconductor pattern 23 a, which is formed along the +Y-side outer edge ofthe substrate 21, and a plurality of rectangular conductor patterns 23 bto 23 i, which are arrayed along the −Y-side outer edge of the substrate21. The conductor patterns 23 a to 23 i are made of metallic materialssuch as copper (Cu), silver (Ag) and so on. In the light emitting device10, the distances among the conductor patterns 23 a to 23 i areapproximately 100 μm or less. The conductor patterns 23 a to 23 i are ina mesh pattern comprised of a plurality of line patterns that areorthogonal to each other. The line width of the line patterns isapproximately 5 μm, and the array pitch is approximately 150 μm.

The conductor patterns constituting the conductor layer 23 are disclosedin detail in US Patent Application Publication No. 2016/0276322(WO/2015/083366). Its content is incorporated herein by reference.

In the light emitting device 10, the substrate 22 is shorter than thesubstrate 21 in the X-axis direction. Consequently, as can be seen byreferring to FIG. 3 , an exposed part 23 j is formed so that the +X-sideend of the conductor pattern 23 a and the conductor pattern 23 iconstituting the conductor layer 23 is exposed.

As shown in FIG. 3 , the resin layer 24 is an insulator that is formedbetween the substrate 21 and the substrate 22. The resin layer 24 isapproximately 50 to 100-μm thick, and made of, for example, atranslucent epoxy thermosetting resin. The resin layer 24 preferably hasa transmittance of 5% or higher, and is made of materials that areprimarily composed of thermosetting resins. The materials to constitutethe resin layer 24 may contain other resin components or the like ifnecessary. Thermosetting resins that are known include epoxy resin,acrylic resin, styrene resin, ester resin, urethane resin, melamineresin, phenol resin, unsaturated polyester resin, diallyl phthalateresin, and so forth.

Also, the resin layer 24 may be made of thermoplastic resins. Thethermoplastic resins that are known include polypropylene resin,polyethylene resin, polyvinyl chloride resin, acrylic resin, Teflonresin (registered trademark), polycarbonate resin, acrylonitrilebutadiene styrene resin, polyamideimide resin, and so forth.

The resin layer 24 according to the present embodiment is also disclosedin detail in US Patent Application Publication No. 2016/0155913(WO2014156159). Its content is incorporated herein by reference.Furthermore, the physical properties of the resin layer 24 such asmechanical loss tangent are disclosed in detail in Japanese PatentApplication No. 2018-164946. Its content is incorporated herein byreference.

The light emitting element 30 ₁ is a square LED chip. As shown in FIG. 5, the light emitting element 30 ₁ is an LED chip of a four-layerstructure, comprised of a base substrate 31, an N-type semiconductorlayer 32, an active layer 33, and a P-type semiconductor layer 34. Avoltage of approximately 2.5 V is applied to the light emitting element30 ₁.

The base substrate 31 is a square plate-like semiconductor substratethat is comprised of GaAs, Si, GaP, and the like. The N-typesemiconductor layer 32 having the same shape as the base substrate 31 isformed on the upper surface of the base substrate 31. Then, the activelayer 33 and the P-type semiconductor layer 34 are stacked, in order, onthe upper surface of the N-type semiconductor layer 32. The active layer33 and the P-type semiconductor layer 34 stacked on the N-typesemiconductor layer 32 have a notch formed in their −Y-side and −X-sidecorner portion, and the surface of the N-type semiconductor layer 32 isexposed from the notch. The N-type semiconductor layer and the P-typesemiconductor layer may be reversed.

In the portion of the N-type semiconductor layer 32 that is exposed fromthe active layer 33 and the P-type semiconductor layer 34, a pad 36,which is electrically connected with the N-type semiconductor layer 32,is formed. In addition, an electrode 35, which is electrically connectedwith the P-type semiconductor layer 34, is formed in the +X-side and+Y-side corner portion of the P-type semiconductor layer 34. Theelectrodes 35 and 36 are made of copper (Cu) and gold (Au), and bumps 37and 38 are formed on their upper surfaces. The bumps 37 and 38 are madeof solder, and shaped like a hemisphere. Metal bumps of gold (Au), agold alloy, and so forth may be used instead of solder bumps. In thelight emitting element 301, the bump 37 functions as a cathodeelectrode, and the bump 38 functions as an anode electrode.

The light emitting element 30 ₁ configured as described above is, asshown in FIG. 6 , arranged between the conductor patterns 23 a and 23 b,the bump 37 is connected to the conductor pattern 23 a, and the bump 38is connected to the conductor pattern 23 b.

The N-type semiconductor layer 32 of the light emitting element 30 ₁faces only the conductor pattern 23 a where the bump 37 is connected,and the P-type semiconductor layer 34 of the light emitting element 30 ₁faces both the conductor pattern 23 a where the bump 37 is connected,and the conductor pattern 23 b where the bump 38 is connected.

Other light emitting elements 30 ₂ to 30 ₈ also have the sameconfiguration as the light emitting element 30 ₁. Then, the lightemitting element 30 ₂ is arranged between conductor patterns 23 b and 23c, and bumps 37 and 38 are respectively connected to the conductorpatterns 23 b and 23 c. Following this in a similar fashion, the lightemitting element 303 is arranged over conductor patterns 23 c and 23 d.The light emitting element 30 ₄ is arranged over conductor patterns 23 dand 23 e. The light emitting element 30 ₅ is arranged over conductorpatterns 23 e and 23 f. The light emitting element 30 ₆ is arranged overconductor patterns 23 f and 23 g. The light emitting element 30 ₇ isarranged over conductor patterns 23 g and 23 h. The light emittingelement 30 ₈ is arranged over conductor patterns 23 h and 23 i. By thismeans, the conductor patterns 23 a to 23 i and the light emittingelements 30 ₁ to 30 ₈ are connected in series. On the light emittingpanel 20, the light emitting elements 30 are arranged at approximately10-mm intervals.

The bumps 37 and 38 to be provided in the light emitting elements 30 arealso disclosed in detail in US Patent Application Publication No.2016/0276561 (WO/2015/083365). Its content is incorporated herein byreference. Also, the electrical connections between the bumps 37 and 38and the conductor layer 23 in the light emitting device are disclosed indetail in Japanese Patent Application No. 2018-16165. Its content isincorporated herein by reference.

FIG. 7 is a side view of the flexible wiring substrate 40. The flexiblewiring substrate 40 is approximately 80-μm thick, and comprised of abase material 41, a conductor layer 43 and a coverlay 42.

The base material 41 is a rectangular member, whose longitudinaldirection runs along the X-axis direction as shown in FIG. 2 . This basematerial 41 is made of polyimide, for example, and a conductor layer 43is formed on its upper surface. The conductor layer 43 is formed bypatterning a copper foil that is stuck on the upper surface ofpolyimide. With the present embodiment, the conductor layer 43 is formedwith two circuit patterns 43 a and 43 b.

The circuit patterns 43 a and 43 b are formed over the base material 41,from the −X-side end to the +X-side end. In the circuit patterns 43 aand 43 b, the −X-side end part is branched into a plurality of parts,and formed in a tapered shape so that the width of the +X-side end partnarrows towards the +X direction.

As shown in FIG. 7 , the conductor layer 43 formed on the upper surfaceof the base material 41 is covered with the coverlay 42 that is bondedby vacuum thermo-compression. This coverlay 42 is shorter than the basematerial 41 in the X-axis direction. Consequently, the −X-side end partsof the circuit patterns 43 a and 43 b constituting the conductor layer43 are exposed. Also, an opening part 42 a is provided in the coverlay42, and the +X-side end parts of the circuit patterns 43 a and 43 b areexposed from this opening part 42 a.

As can be seen by referring to FIG. 4 and FIG. 8 , the flexible wiringsubstrate 40 configured as described above is bonded to the lightemitting panel 20 in a state in which parts of the circuit patterns 43 aand 43 b that are exposed from the coverlay 42 are in contact with the+X-side end parts of the conductor patterns 23 a and 23 i of the lightemitting panel 20. For example, an anisotropic conductive film (ACF) isused to bond the circuit patterns 43 a and 43 b and the conductorpatterns 23 a and 23 i.

The flexible wiring substrate 40 is disclosed in detail in US PatentApplication Publication No. 2016/0276321 (WO/2015/083364). Its contentis incorporated herein by reference.

As shown in FIG. 8 , the gap between the resin layer 24 and thesubstrate 22 that constitute the light emitting panel 20 and the basematerial 41 that constitutes the flexible wiring substrate 40 is filledwith a mold resin 62. The width dl (the size in the X-axis direction) ofthe gap is approximately 2 mm. The mold resin 62 is a resin to contain,as main components, thermoplastic EVA (Ethylene-Vinyl Acetate) resin,polyolefin, synthetic rubber, polyamide, polyester, polyurethane, and soforth. The mold resin 62 is in close contact with the side surfaces ofthe resin layer 24, the substrate 22 and the base material 41, and theconductor layer 23 (conductor patterns 23 a and 23 i), without a gap.

The protective tape 60 is stuck around the joint part 100 of the lightemitting panel 20 and the flexible wiring substrate 40. As shown in FIG.1 , the protective tape 60 is wound around the light emitting panel 20and the flexible wiring substrate 40. The protective tape 60 is made ofa material that is excellent in heat resistance and insulation, such aspolyimide.

As shown in FIG. 2 , a connector 50 is a rectangular parallelepipedcomponent, and is connected with a cable that is routed from a DC powersource. The connector 50 is mounted on the upper surface of the +X-sideend part of the flexible wiring substrate 40. When the connector 50 ismounted on the flexible wiring substrate 40, as shown in FIG. 8 , a pairof terminals 50 a of the connector 50 are respectively connected withthe circuit patterns 43 a and 43 b constituting the conductor layer 43of the flexible wiring substrate 40, through the opening part 42 aprovided in the coverlay 42.

Next, a method for connecting the above-described light emitting panel20 and flexible wiring substrate 40 will be described. When connectingthe light emitting panel 20 and the flexible wiring substrate 40, first,as shown in FIG. 9 , the conductor layer 23 that constitutes the lightemitting panel 20, and the conductor layer 43 of the flexible wiringsubstrate 40, are connected using an anisotropic conductive film 65. Ascan be seen by referring to FIG. 2 , when connecting the conductorlayers 23 and 43, the anisotropic conductive film 65 is provided in thebase material 41 exposing from the coverlay 42 and in the exposed part43 c of the conductor layer 43. The exposed part 23 j of the conductorlayer 23 and the exposed part 43 c of the conductor layer 43 areelectrically connected by the anisotropic conductive film 65.

Next, a hot-melt resin 620, which serves as a resin material, isarranged so as to overlap the boundary between the light emitting panel20 and the flexible wiring substrate 40. To be more specific, thehot-melt resin 620 is arranged over the substrate 22 and the resin layer24 of the light emitting panel 20, and the base material 41 of theflexible wiring substrate 40. As shown in FIG. 10 , the hot-melt resin620 is shaped into a rectangle, whose longitudinal direction runs alongthe Y-axis direction. The dimension of the hot-melt resin 620 in theY-axis direction is equivalent to the width (the dimension in the Y-axisdirection) of the light emitting panel 20.

Next, as shown in FIG. 11 , the protective tape 60 is wound around thejoint part of the light emitting panel 20 and the flexible substrate,and the hot-melt resin 620, to bond these. In this state, the −X-sideend part of the protective tape 60 is bonded to the light emitting panel20, and the +X-side end part is bonded to the flexible wiring substrate40. Therefore, a state is assumed here in which the hot-melt resin 620is arranged in the space defined by the protective tape 60, the lightemitting panel 20 and the flexible substrate.

Next, the hot-melt resin 620 is bonded by thermo-compression to thelight emitting panel 20 and the flexible wiring substrate 40, togetherwith the protective tape 60. By this means, as shown in FIG. 8 , thehot-melt resin 620 serves as the mold resin 62 to fill between the lightemitting panel 20 and the flexible wiring substrate 40 without a gap.The mold resin 62 is in close contact, without a gap, with the sidesurfaces of the resin layer 24, the substrate 22 and the base material41, and with the conductor layers 23 (conductor patterns 23 a and 23 i)that is exposed.

Next, the connector 50 is mounted on the flexible wiring substrate 40.By this means, the light emitting device 10 shown in FIG. 1 iscompleted.

With the light emitting device 10 configured as described above, when aDC voltage is applied to the circuit patterns 43 a and 43 b shown inFIG. 4 via the connector 50, the light emitting elements 30 constitutingthe light emitting panel 20 emit light. The rated voltage of the lightemitting elements 30 is approximately 2.5 V, so that in the lightemitting device 10, a voltage of approximately 20 V is applied to thecircuit patterns 43 a and 43 b.

As described above, with the present embodiment, for example, as shownin FIG. 9 , the hot-melt resin 620 is arranged so as to overlap theboundary between the light emitting panel 20 and the flexible wiringsubstrate 40. Then, along with the protective tape 60 wrapped around andbonded to the joint part of the light emitting panel 20 and the flexiblesubstrate, the hot-melt resin 620 is bonded by thermo-compression to thelight emitting panel 20 and the flexible wiring substrate 40, so thatthe mold resin 62 to fill between the light emitting panel 20 and theflexible wiring substrate 40 can be formed.

Therefore, the mold resin 62 can be formed easily and in a short time,compared to cases in which the mold resin 62 is formed by, for example,potting resin, spreading resin using a dispenser, and so forth. Inaddition, with the present embodiment, the process of forming the moldresin 62 can be carried out in parallel with the therm-compressionbonding process of the protective tape 60. Therefore, the process ofmanufacturing the light emitting device 10 can be simplified, and,consequently, the cost for manufacturing the light emitting device 10can be reduced.

With the present embodiment, the mold resin 62 is filled between thelight emitting panel 20 and the flexible wiring substrate 40, which areconnected with each other. This mold resin 62 is in close contact,without a gap, with the side surfaces of the resin layer 24, thesubstrate 22, and the base material 41, and with the conductor layers 23(conductor patterns 23 a and 23 i) that is exposed. Therefore, theexposed conductor layer 23 is not exposed to outside air orcondensation, so that the corrosion of the conductor layer 23 can bereduced. Consequently, the reliability of the light emitting device 10can be improved.

For example, after the anisotropic conductive film 65 is used for thelight emitting panel 20 and the flexible wiring substrate 40, it may bepossible to use the protective tape 60 alone, to reinforce the jointpart, or to take measures against moisture. However, it is difficult tosufficiently seal the gap between the light emitting panel 20 and theflexible wiring substrate 40, connected with each other, with theprotective tape 60. Consequently, migration-induced dielectricbreakdown, deterioration of the joint part over time, and so forthcannot be reduced sufficiently. With the present embodiment, the moldresin 62 is filled between the light emitting panel 20 and the flexiblewiring substrate, without a gap, so that migration-induced dielectricbreakdown, deterioration of the joint part over time, and so forth canbe reduced sufficiently.

For example, with the light emitting device 10, when the +X-side end ofthe substrate 22 protrudes beyond the resin layer 24 as shown in FIG. 12, or the case where the resin layer 24 protrudes beyond the +X-side endof the substrate 22 as shown in FIG. 13 might occur.

With the present embodiment, in either case shown in FIG. 12 or FIG. 13, the mold resin 62 is formed so as to be in close contact with the sidesurface of the resin layer 24 and the side surface of the substrate 21.Consequently, the conductor layer 23 that is exposed from between thesubstrate 22 of the light emitting panel 20 and the base material 41 ofthe flexible wiring substrate 40 can be sealed hermetically using themold resin 62. Therefore, the dielectric breakdown of the conductorlayer 23 due to migration, the deterioration of the joint part overtime, and so forth can be reduced sufficiently.

In particular, as shown in FIG. 12 , when the substrate 22 protrudeslike an eave, a groove to serve as a passage for the water produced bycondensation is formed. However, with the present embodiment, the moldresin 62 can prevent water from seeping in through the above passage,and improve the reliability of the light emitting device 10.

The mass flow rate (MFR) of the mold resin 62 that constitutes the lightemitting device 10 is preferably 3.0 g/10 min or more and 12.3 g/10 minor less. The reason will be described below.

The present inventors have prepared ten types of samples A to 3 for thelight emitting device 10 shown in FIG. 1 , and tested them. The MFR ofthe mold resin 62 shown in FIG. 8 varies among all of samples A to J.Also, in samples A to 3, the substrates 21 and 22 are 100-μm thick, theresin layer 24 is 60-μm thick, and the flexible wiring substrate 40 is80-μm thick. FIG. 14 is an example of a table showing the test resultsof samples A to J. As shown in FIG. 14 , the MFRs of samples A to J are1.5, 2.0, 3.0, 5.2, 7.2, 9.5, 12.3, 13.0, 30.0 and 50.0 g/10 min,respectively. Ten pieces of each of these samples A to 3 were prepared.

The “normal temperature” section in the table shows the number ofsamples, in each of samples A to J, with which lighting was confirmed ina room-temperature environment (25 to 30° C.). Referring to thenumerical values in the section of normal temperature, the denominatorindicates the number of each type of samples, and the numeratorindicates the number of samples that demonstrated defects such aslighting failures. For example, “0/10” indicates that the number ofsamples that demonstrated defects among ten samples was zero. As shownin the table, in an environment where the temperature is indoortemperature (25 to 30° C.), it was confirmed that ten samples of each often types of samples A to J were normally lit.

Then, for each of samples A to 3, a pressure cooker test (PCT) and awarm-water immersion test were conducted. PCT is a test to applyelectricity to each of samples A to 3 for 24 hours in an environment inwhich the temperature is 121° C. and the humidity is 100%. Furthermore,the warm-water immersion test is a test to apply electricity to each ofsamples A to 3 for 24 hours in 85° C. warm water.

As shown in the table of FIG. 14 , in the PCT and the warm-waterimmersion test, the number of samples C to G with which lighting failureoccurred was zero. Meanwhile, with samples A, B, I and J, there weresamples with which lighting failure occurred, in both the PCT and thewarm-water immersion tests. In addition, sample H had a sample withwhich lighting failure occurred in the warm-water immersion test.Therefore, when the MFR is 3.0 or more and 12.3 or less as with samplesC to G, it is possible to think that water is prevented from seeping inthe joint part of the light emitting panel 20 of the light emittingdevice 10 and the flexible wiring substrate 40. Accordingly, the massflow rate (MFR) of the mold resin 62 is preferably 3.0 g/10 min or moreand 12.3 g/10 min or less.

Now, although an embodiment of the present invention has been describedabove, the present invention is by no means limited to the embodimentdescribed above. For example, a case has been described with the aboveembodiment where, as shown in FIG. 8 , the gap between the resin layer24 and the substrate 22 that constitute the light emitting panel 20 andthe base material 41 that constitutes the flexible wiring substrate 40is filled with the mold resin 62. This is by no means limiting, and, forexample, as shown in FIG. 15 , the gap between the substrate 21 thatconstitutes the light emitting panel 20 and the coverlay 42 thatconstitutes the flexible wiring substrate 40 may be filled with the moldresin 62. By this means, the two boundaries between the light emittingpanel 20 and the flexible wiring substrate 40 are all sealed with themold resin 62. Consequently, migration-induced dielectric breakdown,deterioration of the joint part over time, and so forth can be reducedsufficiently.

As can be seen by referring to FIG. 16 , to manufacture theabove-described light emitting device 10, first, the conductor layer 23that constitutes the light emitting panel 20 and the conductor layer 43of the flexible wiring substrate 40 are connected using the anisotropicconductive film 65. Next, a hot-melt resin 620, which serves as a resinmaterial, is arranged so as to overlap the boundary between the two ofthe light emitting panel 20 and the flexible wiring substrate 40. To bemore specific, a hot-melt resin 620 is arranged over the substrate 22and the resin layer 24 of the light emitting panel 20, and the basematerial 41 of the flexible wiring substrate 40. Similarly, the hot-meltresin 620 is arranged over the substrate 21 that constitutes the lightemitting panel 20 and the coverlay 42 that constitutes the flexiblewiring substrate 40. Next, the protective tape 60 is wound around thejoint part of the light emitting panel 20 and the flexible substrate andthe hot-melt resin 620, to bond these. In this state, the −X-side endpart of the protective tape 60 is bonded to the light emitting panel 20,and the +X-side end part is bonded to the flexible wiring substrate 40.Therefore, a state is assumed here in which two hot-melt resins 620 arearranged in the space defined by the protective tape 60, the lightemitting panel 20 and the flexible substrate.

Next, the two hot-melt resins 620 are bonded by thermo-compression tothe light emitting panel 20 and the flexible wiring substrate 40,together with the protective tape 60. By this means, as shown in FIG. 15, the hot-melt resins 620 become the mold resin 62 to fill between thelight emitting panel 20 and the flexible wiring substrate 40 without agap.

With the above-described embodiment, a light emitting device 10 to haveeight light emitting elements 30 has been described. This is by no meanslimiting, and the light emitting device 10 may have nine or more orseven or fewer light emitting elements.

A case has been described with the above embodiment where the conductorlayer 23 is made of metal. This is by no means limiting, and theconductor layer 23 may be made of a transparent conductive material suchas ITO.

A case has been described with the above embodiment where the resinlayer 24 is formed with no gap between the substrates 21 and 22. This isby no means limiting, and the resin layer 24 may be formed partiallybetween the substrates 21 and 22. For example, the resin layer 24 may beformed only around the light emitting elements.

A case has been described with the above embodiment where the lightemitting panel 20 of the light emitting device 10 has substrates 21 and22 and a resin layer 24. This is by no means limiting, and the lightemitting panel 20 may be comprised only of a substrate 21 and a resinlayer 24 that holds light emitting elements 30.

Although an embodiment of the present invention has been describedabove, the method of manufacturing the light emitting device 10 isdisclosed in detail in US Patent Application Publication No.2017/0250330 (WO/2016/047134). As shown in FIG. 40 , a light emittingdevice, in which light emitting elements are arranged in a matrix shape,is disclosed in detail in Japanese Patent Application No. 2018-164963.Their contents are incorporated herein by reference.

Second Embodiment

Next, a second embodiment will be described below with reference to theaccompanying drawings. Components that are the same as or equivalent tothose of the first embodiment will be assigned the same or equivalentcodes, and their description will be omitted or simplified. The lightemitting device 10 according to the second embodiment is different fromthe light emitting device 10 according to the first embodiment in havinga composite sealing unit 61 comprised of a protective tape 60 and a moldresin 62.

FIG. 17 is a perspective view showing an example of the light emittingdevice 10 according to the present embodiment. As shown in FIG. 17 , thelight emitting device 10 is a device whose longitudinal direction runsalong the X-axis direction. The light emitting device 10 has a lightemitting panel 20 that emits light, a flexible wiring substrate 40 thatis connected with the light emitting panel 20, and a connector 50 thatis mounted on the flexible wiring substrate 40. A composite sealing unit61 is wound around the joint part of the light emitting panel 20 and theflexible wiring substrate 40. The width of the light emitting panel 20is 20 mm.

FIG. 18 is an exploded perspective view of the light emitting device 10.The light emitting panel 20 and the flexible wiring substrate 40 aremembers whose longitudinal direction runs along the X-axis direction.The flexible wiring substrate 40 is 80-μm thick, and comprised of a basematerial 41, which serves as the base, a conductor layer 43, which isformed on the upper surface of the base material 41, and a coverlay 42,which covers the conductor layer 43.

The base material 41 is a rectangular member whose longitudinaldirection runs along the X-axis direction. This base material 41 is madeof polyimide, for example, and a conductor layer 43 is formed on itsupper surface. The conductor layer 43 is formed by patterning a copperfoil that is stuck on the upper surface of the base material 41. Withthe present embodiment, the conductor layer 43 is formed with twocircuit patterns 43 a and 43 b.

The circuit patterns 43 a and 43 b are formed over the base material 41,from the −X-side end to the +X-side end. In the circuit patterns 43 aand 43 b, the −X-side end part is branched into a plurality of parts,and formed in a tapered shape in which the width of the +X-side end partnarrows towards the +X direction.

The conductor layer 43, formed on the upper surface of the base material41, is covered with the coverlay 42 that is bonded by vacuumthermo-compression.

The connector 50 is a rectangular parallelepiped component, and isconnected with a cable routed from a DC power source. The connector 50is mounted on the upper surface of the +X-side end part of the flexiblewiring substrate 40.

The composite sealing unit 61 preferably has excellent heat resistanceand insulation, and is comprised of a protective tape 60, which is madeof materials such as, for example, polyimide, polyester, polyamide,liquid crystal polymer, PEEK (polyetheretherketone) and so on, and amold resin 62.

The light emitting panel 20 according to the present embodiment has thesame configuration as the light emitting panel 20 according to the firstembodiment. As shown in FIG. 3 , the light emitting panel 20 has a pairof substrates 21 and 22, a resin layer 24 that is formed between thesubstrates 21 and 22, and eight light emitting elements 30 ₁ to 30 ₈that are arranged inside the resin layer 24.

The substrates 21 and 22 are rectangular substrates, whose longitudinaldirection runs along the X-axis direction. The substrate 21 is afilm-like member that is approximately 50 to 300-μm thick, and, with thepresent embodiment, a PET film that is 100-μm thick is used. Thesubstrates 21 and 22 are transparent to visible light. The totalluminous transmittance of the substrates 21 and 22 is preferably 5% ormore and 95% or less. Note that the total luminous transmittance refersto the total luminous transmittance measured in conformity with theJapanese Industrial Standard JISK7375: 2008.

Also, the substrates 21 and 22 are flexible, and their bending modulusof elasticity is 0 to 320 kgf/mm², approximately. Note that the bendingmodulus of elasticity is a value that is measured by a method inconformity with JIS K7171: 2016.

As for the materials for the substrates 21 and 22, polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC),polyethylene succinate (PES), cyclic olefin resin, acrylic resin,polyimide, and so forth may be used.

A conductor layer 23, approximately 0.05 μm to 2-μm thick, is formed inthe lower surface of the substrate 21 (the surface on the −Z side)between the pair of substrates 21 and 22.

The resin layer 24 is an insulator formed between the substrate 21 andthe substrate 22. The resin layer 24 is approximately 50 to 150-μmthick, and made of, for example, an epoxy thermosetting resin, apolyimide thermosetting resin and so forth, which are translucent. Theresin layer 24 preferably has a transmittance of 5% or higher, and ismade of materials that are primarily composed of thermosetting resins.The materials to constitute the resin layer 24 may contain other resincomponents or the like if necessary. As for the thermosetting resins,epoxy resin, acrylic resin, styrene resin, ester resin, urethane resin,melamine resin, phenol resin, unsaturated polyester resin, diallylphthalate resin, polyimide and so forth may be used.

The resin layer 24 may be made of resins containing thermoplastic resinsas main components. The thermoplastic resins may include polypropyleneresin, polyethylene resin, polyvinyl chloride resin, acrylic resin,Teflon resin (registered trademark), polycarbonate resin, acrylonitrilebutadiene styrene resin, polyamideimide resin, and so forth.

The resin layer 24 according to the present embodiment is also disclosedin detail in US Patent Application Publication No. 2016/0155913(WO2014156159). Its content is incorporated herein by reference.Furthermore, the physical properties of the resin layer 24 such asmechanical loss tangent are disclosed in detail in Japanese PatentApplication No. 2018-164946. Its content is incorporated herein byreference.

In the light emitting device 10, the substrate 22 is shorter than thesubstrate 21 in the X-axis direction. Consequently, the +X-side end ofthe conductor layer 23 is exposed.

FIG. 19 is a plan view of the light emitting device 10. As can be seenby referring to FIG. 19 , the conductor layer 23 is comprised of anL-shaped conductor pattern 23 a, which is formed along the +Y-side outeredge of the substrate 21, and a plurality of rectangular conductorpatterns 23 b to 23 i, which are arrayed along the −Y-side outer edge ofthe substrate 21. The conductor patterns 23 a to 23 i are made ofmetallic materials such as copper (Cu), silver (Ag) and so on. In thelight emitting device 10, the distances among the conductor patterns 23a to 23 i are approximately 100 μm or less. The conductor patterns 23 ato 23 i are in a mesh pattern comprised of a plurality of line patternsthat are orthogonal to each other. The line width of the line patternsis approximately 5 μm, and the array pitch is approximately 150 μm.

The conductor layer 23 is by no means limited to a mesh pattern, and mayassume a stripe pattern, a honeycomb pattern and so forth, or may be,furthermore, a patterned transparent conductor film or the like. Theconductor layer 23 has only to be a material having a total luminoustransmittance of 5% or more and 95% or less, and a sheet resistance of100 Ω/sq or less.

The conductor patterns to constitute the conductor layer 23 aredisclosed in detail in US Patent Application Publication No.2016/0276322 (WO/2015/083366). Its content is incorporated herein byreference.

The light emitting elements 30 ₁ to 30 ₈ according to the presentembodiment have the same configuration as the light emitting elements 30₁ to 30 ₈ according to the first embodiment. As can be seen by referringto FIG. 5 , the light emitting elements 30 ₁ to 30 ₈ are square LEDchips, and LED chips of a four-layer structure, comprised of a basesubstrate 31, an N-type semiconductor layer 32, an active layer 33, anda P-type semiconductor layer 34.

The bumps 37 and 38 to be provided in the light emitting element 30 arealso disclosed in detail in US Patent Application Publication No.2016/0276561 (WO/2015/083365). Its content is incorporated herein byreference. Also, the electrical connection between the bumps 37 and 38and the conductor layer 23 in the light emitting device is disclosed indetail in Japanese Patent Application NO. 2018-16165. Its content isincorporated herein by reference.

As can be seen by referring to FIG. 6 , the light emitting element 30 ₁is arranged between the conductor patterns 23 a and 23 b, the bump 37 isconnected to conductor pattern 23 a, and the bump 38 is connected to theconductor pattern 23 b.

The N-type semiconductor layer 32 of the light emitting element 30 ₁faces only the conductor pattern 23 a where the bump 37 is connected,and the P-type semiconductor layer 34 of the light emitting element 30 ₁faces both the conductor pattern 23 a where the bump 37 is connected andthe conductor pattern 23 b where the bump 38 is connected.

Other light emitting elements 30 ₂ to 30 ₈ also have the sameconfiguration as the light emitting element 30 ₁. Then, the lightemitting element 30 ₂ is arranged between conductor patterns 23 b and 23c, and bumps 37 and 38 are respectively connected to the conductorpatterns 23 b and 23 c. Following this in a similar fashion, the lightemitting element 303 is arranged over conductor patterns 23 c and 23 d.The light emitting element 30 ₄ is arranged over conductor patterns 23 dand 23 e. The light emitting element 30 ₅ is arranged over conductorpatterns 23 e and 23 f. The light emitting element 30 ₆ is arranged overconductor patterns 23 f and 23 g. The light emitting element 30 ₇ isarranged over conductor patterns 23 g and 23 h. The light emittingelement 30 ₈ is arranged over conductor patterns 23 h and 23 i. By thismeans, the conductor patterns 23 a to 23 i and the light emittingelements 30 ₁ to 30 ₈ are connected in series. In the light emittingpanel 20, light emitting elements 30 are arranged at approximately 10-mmintervals.

The flexible wiring substrate 40 according to the present embodiment hasa configuration equivalent to that of the flexible wiring substrate 40according to the first embodiment. As can be seen by referring to FIG. 7, the coverlay 42 of the flexible wiring substrate 40 is shorter thanthe base material 41 in the X-axis direction. Consequently, the −X-sideend part of the conductor layer 43 is exposed.

The flexible wiring substrate 40 is disclosed in detail in US PatentApplication Publication No. 2016/0276321 (WO/2015/083364). Its contentis incorporated herein by reference.

As shown in FIG. 20 , the flexible wiring substrate 40 is bonded to thelight emitting panel 20, in a state in which the conductor layer 43,which is exposed from the coverlay 42, is in contact with the +X-sideend part of the conductor layer 23 of the light emitting panel 20. Forexample, an anisotropic conductive film (ACF) 65 is used to bond theconductor layer 43 and the conductor layer 23. For the anisotropicconductive film 65, for example, a thermosetting adhesive, which has afilm thickness of approximately 25 μm, and in which, for example, Nihaving a particle diameter of approximately 2 μm is mixed as aconductive material, can be used. Furthermore, instead of an anisotropicconductive film, an anisotropic conductive paste, an anisotropicconductive ink, and so forth may be used to bond between the conductorlayer 43 and the conductor layer 23. The anisotropic conductive pasteand the anisotropic conductive ink can be applied to the joint part ofthe conductor layer 43 and the conductor layer 23 by printing, by usingink jet, and so on.

The anisotropic conductive film (ACF) 65 is disclosed in US PatentApplication Publication No. 2016/0276321 (WO/2015/083364). Its contentis incorporated herein by reference.

The gap between the resin layer 24 and substrate 22 that constitute thelight emitting panel 20 and the base material 41 that constitutes theflexible wiring substrate 40 is filled with a mold resin 62. Thedistance dl of the above gap (the size in the X-axis direction) isapproximately 2 mm. The mold resin 62 constitutes the composite sealingunit 61 together with the protective tape 60. The mold resin 62 is aresin that constitutes the adhesive layer of the composite sealing unit61.

The mold resin 62 is a thermosetting resin. Epoxy resin, acrylic resin,styrene resin, ester resin, urethane resin, melamine resin, phenolresin, unsaturated polyester resin, diallyl phthalate resin, polyimideand the like can be used as thermosetting resin for the mold resin 62.The minimum melt viscosity of the mold resin 62 is 1.0 E+0.5 Pa·s orless. The mold resin 62 is in close contact with the side surfaces ofthe resin layer 24, the substrate 22 and the base material 41, and theconductor layer 23 (conductor patterns 23 a and 23 i), without a gap.

The mold resin 62 may be a thermoplastic resin. For the thermoplasticresin, polypropylene resin, polyethylene resin, polyvinyl chlorideresin, acrylic resin, Teflon resin (registered trademark), polycarbonateresin, acrylonitrile butadiene styrene resin, polyamideimide resin, andso forth can be used. A hot-melt adhesive may be used as the mold resin62. Adhesives of ethylene vinyl acetate type, olefin type, rubber type,polyamide type such as polyester, and polyurethane type, or or athermoplastic olefin polymer such as propylene, or those obtained bycopolymerizing propylene and ethylene, propylene and butene-1, and soforth can be used as hot-melt adhesives.

When the connector 50 is mounted on the flexible wiring substrate 40, apair of terminals 50 a of the connector 50 are respectively connectedwith the circuit patterns 43 a and 43 b constituting the conductor layer43 of the flexible wiring substrate 40, through the opening part 42 aprovided in the coverlay 42.

Next, the procedures for connecting the light emitting panel 20 and theflexible wiring substrate 40 in the light emitting device 10 describedabove will be described.

First, referring to FIG. 21 , an anisotropic conductive film 65 isarranged in end parts of the conductor patterns 23 a and 23 i thatexpose from the +X-side end part of the light emitting panel 20. Theanisotropic conductive film 65 is arranged over the conductor patterns23 a and 23 i. Then, as shown in FIG. 22 , the conductor patterns 23 aand 23 i of the conductor layer 23 that constitute the light emittingpanel 20 and the conductive layer 43 that is exposed from the end partof the flexible wiring substrate 40 are bonded by thermo-compressionusing the anisotropic conductive film 65, so that electrical contact isachieved.

With the light emitting device 10, the joint part 100 of the lightemitting panel 20 and the flexible wiring substrate 40 is sealed withthe mold resin 62 and their outer periphery is covered with theprotective tape 60, thereby achieving sealing of high mechanicalreliability. To do so, the joint part 100 is covered with the mold resin62 by applying the mold resin 62 to the joint part 100, winding the moldresin 62, and so on.

After the protective tape 60 is wound around the mold resin 62, the moldresin 62 may be heated, bonded by thermo-compression, or bonded byvacuum thermo-compression, but, when doing so, voids are likely toremain between the protective tape 60 and the mold resin 62.Consequently, there is a possibility that problems such as moistureseeping into the joint part 100 might arise.

Therefore, as shown in FIG. 23 , a composite sealing material 63 that islong enough to be wound around the joint part 100 is prepared. Thiscomposite sealing material 63 is a member to serve as the compositesealing unit 61 by way of thermo-compression bonding. The compositesealing material 63 is comprised of a protective tape 60 and a moldresin 62 that serves as an adhesive layer. The thickness of the moldresin 62 that constitutes the composite sealing material 63 is adjustedby, for example, stacking 20-μm thick resin sheets. The thickness of themold resin 62 is, for example, 60 μm to 120 μm. In this way, thecomposite sealing material 63, in which a protective tape 60 and a moldresin 62 are stacked in advance, is wound around the joint part 100 andthen bonded by vacuum thermo-compression, so that the joint part 100with no remaining voids can be formed in a small number of steps.

As shown in FIG. 24 , the composite sealing material 63 is wound aroundthe joint part 100 of the light emitting panel 20 and the flexiblewiring substrate 40. The composite sealing material 63 needs to be longenough to wrap around the light emitting panel 20 and the flexiblewiring substrate 40 once when the composite sealing material 63 is woundaround the joint part 100 of the light emitting panel 20 and theflexible wiring substrate 40. To be more specific, looking at oneposition among positions P0 to P3 in the portion where the compositesealing unit 61 is wound around, the value of 2πR (the length of theentire circumference) of the length of the composite sealing unit 61 inthat position needs to show a length that is long enough to wrap aroundthe light emitting panel 20 and the flexible wiring substrate 40 by1.125 times or more and 1.8755 times or less. This is because, if thelength of the composite sealing unit 61 is below this range, problemssuch as water seeping into the joint part 100 are likely to arise, and,if the length of the composite sealing unit 61 is beyond this range, theflexibility of the light emitting device 10 is likely to be damagedseverely.

When the composite sealing material 63 is wound around the lightemitting panel 20 and the flexible wiring substrate 40, as shown in FIG.25 , the composite sealing material 63 is fixed to the light emittingpanel 20 and the flexible wiring substrate 40 on a temporary basis. Tofix the composite sealing material 63 on a temporary basis, an adhesivemay be applied to the composite sealing material 63 or the mold resin62, separately, before the composite sealing material 63 is wound.

Next, the composite sealing material 63 is bonded, bythermo-compression, to the light emitting panel 20 and the flexiblewiring substrate 40. By this means, the mold resin 62 of the compositesealing material 63 fills between the light emitting panel 20 and theflexible wiring substrate 40, with no gap, as shown in FIG. 26 . Themold resin 62 is in close contact, without a gap, with the side surfacesof the resin layer 24, the substrate 22 and the base material 41, andwith the conductor layers 23 (conductor patterns 23 a and 23 i) that isexposed.

With the light emitting device 10 described above, when a DC voltage isapplied to the circuit patterns 43 a and 43 b shown in FIG. 19 via theconnector 50, the light emitting elements 30 that constitute the lightemitting panel 20 emit light. With the light emitting device 10, avoltage of approximately 20 V is applied to the circuit patterns 43 aand 43 b.

As described above, with the present embodiment, when manufacturing thelight emitting device 10, for example, as shown in FIG. 25 , a compositesealing material 63 is wound around the joint part 100 of the lightemitting panel 20 and the flexible wiring substrate 40. Next, thecomposite sealing material 63 is bonded, by thermo-compression, to thelight emitting panel 20 and the flexible wiring substrate 40. Havingundergone the above steps, the mold resin 62 fills between the lightemitting panel 20 and the flexible wiring substrate 40.

This mold resin 62 is in close contact, without a gap, with the sidesurfaces of the resin layer 24, the substrate 22, and the base material41, and with the conductor layers 23 (conductor patterns 23 a and 23 i)that is exposed. Therefore, the conductor layer 23 that is exposed isnot exposed to outside air or condensation, so that the corrosion of theconductor layer 23, migration-induced dielectric breakdown and so forthcan be reduced, and, consequently, deterioration of the joint part 100over time can be reduced. Consequently, the reliability of the lightemitting device 10 can be improved.

Note that, with the present embodiment, the composite film materialformed by stacking a protective tape 60 and a mold resin 62 was referredto as a “composite sealing material 63,” and the portion that is definedinside the light emitting device 10 after being wound around the jointpart 100 of the light emitting panel 20 and the light emitting device 10and processed was referred to as a “composite sealing unit 61.”

The gap length dl between the light emitting panel 20 and the flexiblewiring substrate 40 in FIG. 20 is preferably 1 mm or more and 5 mm orless, and, more preferably, 1.5 mm or more and 3 mm or less. The reasonis, when the composite sealing material 63, which serves as thecomposite sealing unit 61, is bonded by vacuum thermo-compression, themold resin 62 that is deformed and spreads fills voids near the jointpart 100, and the buffering effect of this prevents the deformation ofthe joint part 100, and, as a result of this, the reliability of thejoint part is improved, and the penetration of water from outside isprevented. Furthermore, if the gap length dl is less than 1 mm, it ismore likely that enough mold resin 62 is not filled there, and thereforevoids are produced. Furthermore, when the gap length dl exceeds 5 mm,the bonding of the gap portion becomes weak, and peeling or crackingoccurs under severe use conditions such as when repeated stress isapplied, and the long-term reliability is damaged.

For example, after the light emitting panel 20 and the flexible wiringsubstrate 40 are bonded using the anisotropic conductive film 65, it maybe possible to use the protective tape 60 alone, to reinforce the jointpart 100, or to take measures against moisture. However, it is difficultto seal, sufficiently, the gap between the light emitting panel 20 andthe flexible wiring substrate 40 that are connected with each other,with the protective tape 60 alone. Consequently, migration-induceddielectric breakdown, deterioration of the joint part 100 over time, andso forth cannot be reduced sufficiently. With the present embodiment,the mold resin 62 is filled between the light emitting panel 20 and theflexible wiring substrate without a gap, so that migration-induceddielectric breakdown, deterioration of the joint part 100 over time andso forth can be reduced sufficiently.

In addition, the mold resin 62 can be formed easily and in a short time,compared to cases in which the mold resin 62 is formed by, for example,potting resin, spreading resin using a dispenser, and so forth.Furthermore, with the present embodiment, the process of forming themold resin 62 can be carried out in parallel with the thermalcompression bonding process of the composite sealing material 63.Therefore, the process of manufacturing the light emitting device 10 canbe simplified, and, furthermore, the cost for manufacturing the lightemitting device 10 can be reduced.

The thickness of the mold resin 62 of the composite sealing material 63is preferably 60 μm or more, and, more preferably, 80 μm or more. Bymaking the thickness of the mold resin 62 of the composite sealingmaterial 63 60 μm or more, it is possible to prevent moisture and thelike from seeping into the joint part 100 of the light emitting panel 20and the flexible wiring substrate 40. Furthermore, by making thethickness the mold resin 62 of the composite sealing material 63 80 μmor more, it is possible to prevent, nearly completely, moisture and thelike from seeping into the joint part 100 of the light emitting panel 20and the flexible wiring substrate 40.

With the light emitting device 10, the thickness of the mold resin 62 ofthe composite sealing material 63 is preferably thin, from theperspective of ensuring flexibility. With the present embodiment, theflexibility of the light emitting device 10 can be maintained by makingthe thickness of the mold resin 62 of the composite sealing material 63160 μm or less.

When the mold resin 62 of the composite sealing unit 61 isthermo-compression-bonded, its thickness becomes approximately 80%.Therefore, the thickness of the mold resin 62 of the light emittingdevice 10 is preferably 56 μm or more, and, more preferably, 64 μm ormore. Also, the thickness of the mold resin 62 of the light emittingdevice 10 is preferably 128 μm or less. Therefore, the thickness of thethickest part of the light emitting device 10, including the compositesealing unit 61, in the joint part 100 of the light emitting panel 20and the flexible wiring substrate 40 needs to be equal to or greaterthan the value adding 138 μm to the thickness of the light emittingpanel 20, and needs to be less than or equal to the value adding 446 μmto the thickness of the light emitting panel.

The optimum value for the thickness of the mold resin 62 determined asdescribed above varies depending on the sum of the thickness of thesubstrate 22 and the thickness of the resin layer 24. With the lightemitting device 10, the sum of the thickness of the substrate 22 and thethickness of the resin layer 24, or “SUM,” is approximately 220 μm. Withthe light emitting device 10, the thickness of the mold resin 62 may besmaller than SUM, and the thickness of the mold resin 62 is preferably25% or more and 58% or less of SUM, and, more preferably, 29% or moreand 58% or less.

Similarly, the optimum value for the thickness of the mold resin 62varies depending on the thickness of the flexible wiring substrate 40.With the light emitting device 10, the flexible wiring substrate 40 isapproximately 80-μm thick. With the light emitting device 10, thethickness of the mold resin 62 is preferably 70% or more and 160% orless, of the thickness of the flexible wiring substrate 40, and, morepreferably, 80% or more and 160% or less.

The light emitting device 10 with the protective tape 60 and the moldresin 62 can maintain the adhesion strength high near the joint part 100of the light emitting panel 20 and the flexible wiring substrate 40. Bythis means, it is possible to prevent the light emitting panel 20 andthe flexible wiring substrate 40 from parting.

With the light emitting device 10, as shown in FIG. 20 , the distance dlbetween the substrate 22 and the flexible wiring substrate 40 isapproximately 2 mm. The thickness of the mold resin 62 is preferably 2%or more and 5% or less of the distance dl, and, more preferably, 3% ormore and 5% or less.

Now, although embodiments of the present invention have been describedabove, the present invention is by no means limited to the embodimentsdescribed above. For example, with the above embodiments, light emittingdevices 10 to have eight light emitting elements 30 connected in serieshave been described. This is by no means limiting, and a light emittingdevice 10 may have nine or more or seven or fewer light emittingelements. A light emitting device 10 may have a plurality of lightemitting elements 30 that are connected in parallel. Also, a lightemitting device 10 may have a plurality of light emitting elements 30,where light emitting elements 30 connected in series and light emittingelements 30 connected in parallel are mixedly present.

A case has been described with the above embodiment where the conductorlayer 23 is made of metal. This is by no means limiting, and theconductor layer 23 may be made of a transparent conductive material suchas ITO.

A case has been described with the above embodiment where bumps 37 and38 are formed on the electrodes 35 and 36 of light emitting elements 30.This is by no means limiting, and the bumps 37 and 38 may not be formedon the electrodes 35 and 36 of light emitting elements 30.

In the above embodiments, a pair of electrodes 35 and 36 were formed onthe surface of a light emitting element 30 on one side. This is by nomeans limiting, and a light emitting element 30 may be a light emittingelement that has electrodes on the surface on one side and on thesurface on the other side. In this case, a conductor layer is alsoformed on the substrate 22.

As shown in FIG. 35 , in practice, the substrates 21 and 22 are shapedto curve along the light emitting elements 30. To be more specific, thethickness T2 of the resin layer 24 is smaller than the height T1 of thelight emitting elements 30 ₁ to 30 ₈ so as to place the conductor layer23 and the bumps 37 and 38 in good contact with each other. Thesubstrates 21 and 22 that are in close contact with the resin layer 24have curved shapes so that the parts where the light emitting elements30 ₁ to 30 ₈ are arranged protrude outward and the parts in between thelight emitting elements 30 ₁ to 30 ₈ are depressed. Because thesubstrates 21 and 22 are curved in this way, the conductor layer 23 isin a state of being pressed against the bumps 37 and 38 by thesubstrates 21 and 22.

Cases have been described with the above embodiments where a resin layer24 is formed, with no gap, between substrates 21 and 22. This is by nomeans limiting, and the resin layer 24 may be formed between thesubstrates 21 and 22 only partially. For example, the resin layer 24 maybe formed only around light emitting elements. For example, as shown inFIG. 36 , the resin layer 24 may be formed so as to constitute a spacerto surround light emitting elements 30.

Cases have been described with the above embodiments where the lightemitting panel 20 of a light emitting device 10 has a pair of substrates21 and 22 and a resin layer 24. This is by no means limiting, and, asshown in FIG. 37 , a light emitting panel 20 may be comprised of onesubstrate 21, and a resin layer 24 that holds light emitting elements30.

There may be cases where, in a light emitting device 10, the lightemitting panel 20 and the flexible wiring substrate 40 are not arrangedon the same plane. Especially when the light emitting device 10 ismounted on a vehicle, it is often the case that the light emitting panel20 and wiring/circuit portions such as the flexible wiring substrate 40are not arranged on the same plane. In such cases, it is necessary toconsider that the joint part 100 of the light emitting panel 20 and theflexible wiring substrate 40 is pulled in directions to part from theplane on which the light emitting panel 20 is arranged, and/or that abending stress is applied repetitively to the joint part 100 of thelight emitting panel 20 and the flexible wiring substrate 40.

In addition, when using the light emitting device 10 to be mounted on avehicle, it is also necessary to take into account that impacts due tohigh temperature and high humidity also apply, in addition to and at thesame time with the above stress. Consequently, both the stress thatapplies to the light emitting device 10 and the impact of use in ahigh-temperature and high-humidity environment on the light emittingdevice 10 need to be taken into account when making an evaluation. Toensure the reliability of the light emitting device 10 for mounting on avehicle, as for the tensile stress, the light emitting device 10 needsto withstand application of a 16-N tensile stress, and, as for repeatedbending (vibration), the light emitting device 10 needs to withstand1000 times of repeated bending at 4 N, and, furthermore, the lightemitting device 10 must operate normally even after 1000 hours ofoperation under the conditions of 85° C. temperature and 85% humidity.From this perspective, the following tests have been conducted for thelight emitting device 10 according to the present embodiment.

Hereinafter, testing and evaluation methods that have been conducted forthe light emitting device 10 according to the present embodiment will bedescribed.

<Infiltration Search Test>

An infiltration search test was conducted on the light emitting device10 obtained then, substantially in compliance with JIS Z 2343-1, “Part1: General principles—Method for liquid penetrant testing andclassification of the penetrant indication” and JIS Z 2343-2, “Part 2:Testing of penetrant materials.” To be more specific, an R-3B (NT)water-washable penetrant manufactured by Eishin Kagaku Co., Ltd. wasused, and the light emitting device 10 was immersed in this penetrantfor 24 hours under vacuum, and then immersed in the penetrant for 24hours under normal pressure. Immediately after this, microscopicobservation was made from the upper surface of the joint part 100, andwhether or not the penetrant had infiltrated was checked. The number ofspecimens was five.

<Cross-Sectional Void Observation Test>

A cross-sectional void observation test for the light emitting device 10was conducted. In the cross-sectional void observation test, after thelight emitting device 10 was cut along the line AA of FIG. 20 , the cutplane, polished, was observed with an optical microscope, and whether ornot there were voids in regions on the inner side of the protective tape60 was checked. The number of specimens was five.

<Average 90-Degree Peeling Durability Test>

An average 90-degree peeling durability test was conducted for the lightemitting device 10. The testing method was basically the same as the90-degree peeling test in compliance with JIS K 6854-1: 1999. In the90-degree peeling test, as shown in FIG. 28 and FIG. 31 , the lightemitting panel 20 was placed on a sturdy surface plate, and thesubstrate 21 was bonded to the surface plate. Regarding the bonding ofthe substrate 21, the +X-side region from position Q2 in FIG. 28 or the+X-side region from position P3 in FIG. 31 was bonded to the surfaceplate, to keep the horizontal state. Then, the flexible wiring substrate40 was peeled from the light emitting panel 20 by pulling the flexiblewiring substrate 40 vertically upward, and, meanwhile, the durabilityagainst peeling (N/cm) was measured at each position.

In the average 90-degree peeling durability test, a 90-degree peelingmeasurement machine by Nissin Kagaku Kabushiki Kaisha was used for thepeeling measurement machine. A measurement machine by Aikoh EngineeringCo., Ltd., model 9520, was used for the strength measurement machine. Acollector by Keyence Corporation, model GR-3500, was used for the datacollector. Furthermore, the direction of peeling was 90 degrees, thewidth of peeling was 5 mm, the speed of peeling was 24 mm/sec, and thesampling time was 50 ms/s.

The position where the measurement was started was position Q1 in FIG.28 , or position P0 in FIG. 31 . That is, when the light emitting device10 had no mold resin 62 or protective tape 60, the point where theanisotropic conductive film 65 started peeling from the conductor layer23 or the substrate 21 was the position the measurement was started.Also, when the light emitting device 10 had a mold resin 62 and aprotective tape 60, the point where the mold resin 62 started peelingfrom the coverlay 42 was the position the measurement was started. Theposition where the measurement was finished was the point in the jointpart 100 where the electrical contact between the anisotropic conductivefilm 65 and the conductor layer 23 was cut. The starting point wasdetermined visually, and the end point was determined from changes inthe electrical resistance of the conductor layer 43 and the conductorlayer 23.

The average value of adhesion strength (N/cm) from the starting positionto the end position was defined as the average 90-degree peelingdurability of the light emitting device 10. Note that, when theprotective tape 60 was wound around the joint part 100 and its vicinity,or, to be more specific, when the protective tape 60 was wound aroundthe portion of position P0 or position P3 in the light emitting device10 illustrated in FIG. 31 , both ends of the protective tape 60 whenseeing the light emitting device 10 into the −Z direction were cut inadvance along the broken lines, as shown in FIG. 30 , and the test wasconducted. By so doing, the test was conducted in a state in which theprotective tape 60 was separated vertically. The number of specimens inthis test was five.

FIG. 29 is a diagram showing the result of the peeling test conductedwith the light emitting device 10 shown in FIG. 28 , which has noprotective tape 60 or mold resin 62 attached to the joint part 100. Asshown in FIG. 29 , in the range from position Q1 at the −X-side end toposition Q2 at the +X-side end of the joint part 100, the strength ofadhesion is 4 N/cm or less. In addition, there are locations where theadhesion strength increases temporarily, such as one below position Q1and one above position Q2, but the adhesion strength is 4 N/cm or lessin other locations.

Note that the peeling test of the light emitting panel 20 and theflexible wiring substrate 40 was also conducted without cutting bothends of the protective tape 60. In this case, although the peelingdurability was 15 N/cm or more in all places, this method was notemployed because the amount of deformation of the light emitting device10 was significant, the measured values varied significantly, and soforth, and therefore the accurate peeling strength between the lightemitting panel 20 and the flexible wiring substrate 40 could not bemeasured.

<Adhesion Strength Test>

A test for the adhesion strength of the light emitting device 10 wasconducted. In this case, too, the testing method was basically the sameas the 90-degree peeling test in compliance with JIS K 6854-1: 1999. Inthe adhesion strength test, as shown in FIG. 28 and FIG. 31 , a lightemitting panel 20 was placed on a sturdy surface plate, and a substrate21 was bonded to the surface plate. Regarding the bonding of thesubstrate 21, the +X-side region from position Q2 in FIG. 28 or the+X-side region from position P3 in FIG. 31 was bonded to the surfaceplate, to keep the horizontal state.

Then, the flexible wiring substrate 40 was peeled from the lightemitting panel by pulling the flexible wiring substrate 40 verticallyupward, and, meanwhile, the adhesion strength (N/cm) was measured ateach position. Next, as shown in FIG. 29 and FIG. 32 , the relationshipbetween adhesion strength (N/cm) and the peeling position was plotted,and, after peeling was started, the average value of adhesion strength(N/cm) from the point where the adhesion strength maximized first to thepoint where the adhesion strength minimized first was calculated, andthis was determined as the adhesion strength of the light emittingdevice 10.

Note that, when the protective tape 60 was wound around the joint part100 and its vicinity, or, to be more specific, when the protective tape60 was wound around the portion of position P0 or position P3 in thelight emitting device 10 illustrated in FIG. 31 , both ends of theprotective tape 60 when seeing the light emitting device 10 into the −Zdirection were cut along the broken lines, as shown in FIG. 30 , and thetest was conducted. By so doing, the test was conducted in a state inwhich the protective tape 60 was separated vertically. The number ofspecimens in this test was five.

<Joint-Part Tensile-Reliability Test>

A test for the tensile reliability of the joint part of the lightemitting device 10 was conducted. In this test of the tensilereliability of the joint part, as shown in FIG. 31 , a light emittingpanel 20 was placed on a sturdy surface plate, and a substrate 21 wasbonded to the surface plate. As for the bonding of the substrate 21, the+X-side region from position Q2 in FIG. 28 or the +X-side region fromposition P3 in FIG. 31 was bonded to the surface plate, to maintain thehorizontal state. Then, first, the flexible wiring substrate 40 waspulled vertically upward so that the tensile stress reaches from 0 N to16 N in four seconds, and, after the flexible wiring substrate 40 washeld, for five seconds, in a state in which the tensile stress was 16 N,the stress was released. This operation was repeated 5 times. Note that,unlike the average 90-degree peeling durability test, the test wasconducted without cutting the protective tape 60.

After that, twenty light emitting devices 10 were left for 500 hours inan environment in which the temperature was 85° C. and the humidity was85%, another twenty light emitting devices 10 were left for 1000 hours,and then electricity was applied to the light emitting devices 10. Then,the number of light emitting devices 10 in which none of the lightemitting elements 30 on the light emitting panel 20 failed to light wascounted.

<Joint-Part Repeated-Bending Reliability Test>

A test for the repeated-bending reliability of the joint part of thelight emitting device 10 was conducted. In this test of the tensilereliability of the joint part, as shown in FIG. 31 , a light emittingpanel 20 was placed on a sturdy surface plate, and a substrate 21 wasbonded to the surface plate. As for the bonding of the substrate 21, the+X-side region from position Q2 in FIG. 28 or the +X-side region fromposition P3 in FIG. 31 was bonded to the surface plate, to maintain thehorizontal state. First, the flexible wiring substrate 40 was pulledvertically upward so that the tensile stress reaches from 0 N to 4 N infive seconds. Next, the flexible wiring substrate 40 was extended sothat the tensile stress reaches from 4 N to 0 N in five seconds. Thesetwo actions make up one set, and this set was repeated 1000 times.

Note that, unlike the average 90-degree peeling durability test, thetest was conducted without cutting the protective tape 60. After that,twenty light emitting devices 10 were left for 500 hours in anenvironment in which the temperature was 85° C. and the humidity was85%, another twenty light emitting devices 10 were left for 1000 hours,and then electricity was applied to the light emitting device 10. Then,the number of light emitting devices 10 in which none of the lightemitting elements 30 on the light emitting panel 20 failed to light wascounted.

EXAMPLES

Next, specific examples and their evaluation results will be described.

Examples 1 to 4

In the light emitting panel 20 and the flexible wiring substrate 40according to the above-described embodiments, as shown in FIG. 21 , ananisotropic conductive film 65 with a separator was placed in end partsof the conductor patterns 23 a and 23 i that expose from +X-side endpart of the light emitting panel 20, and the anisotropic conductive film65 was bonded by thermo-compression at 160° C. for ten seconds. Afterthat, the separator was peeled off. By this means, the anisotropicconductive film 65 was arranged over the conductor patterns 23 a and 23i.

Next, as shown in FIG. 22 , the conductor patterns 23 a and 23 i of theconductor layer 23 to constitute the light emitting panel 20 and theconductor layer 43 that is exposed from the end part of the flexiblewiring substrate 40 are bonded by thermo-compression via the anisotropicconductive film 65, so that electrical contact is achieved between theconductor layer 23 and the conductor patterns 23 a and 23 i.

Next, four types of composite sealing materials 63, having differentthicknesses of the mold resin 62, are prepared in such a length that itcan be wound 1.5 times around the joint part 100 of the light emittingpanel 20 and the flexible wiring substrate 40. Then, the compositesealing material 63 was wound around the joint part 100 of the lightemitting panel 20 and the flexible wiring substrate 40, and then bondedby vacuum thermo-compression.

A polyimide film was used for the protective tape 60 for the compositesealing material 63, and an epoxy thermosetting resin was used for themold resin 62. For the light emitting devices 10 according to examples 1to 4, composite sealing materials 63 with mold resins 62 that were 60-μmthick, 80-μm thick, 100-μm thick and 120-μm thick were used,respectively. The joint part 100 was sealed by using composite sealingmaterials 63 (see FIG. 23 ), in which the mold resin 62 was stacked onthe protective tape 60 and integrated in advance.

110 light emitting devices were manufactured following theabove-described procedures, for each of the light emitting devices 10Ato 10D according to examples 1 to 4. Then, for each of the four types oflight emitting devices 10A to 10D, the cross-sectional void observationtest and the infiltration search test, which have been described earlierherein, were conducted, using five light emitting devices each. Theresults are shown in FIG. 27 . In all of the light emitting devices 10Ato 10D, no void was found by observing cross-sections, and, furthermore,no infiltration of the infiltration solution was observed in theinfiltration search test.

Similarly, the above-described average 90-degree peeling durability testand the adhesion strength test were conducted on ten light emittingdevices for each. FIG. 32 is a diagram showing the result of the peelingdurability test conducted for the light emitting device 10A of example 1shown in FIG. 31 . As shown in FIG. 32 , the adhesion strength may fallto 4 N/cm or below in places between position P1 on the −X-side end andposition P2 on the +X-side end of the joint part 100. However, theadhesion strength is always twice 4 N/cm or more in places from positionP1 and below, down to position P0, or in places from position P2 andabove, up to position P3. Note that position P0 is the −X-side endposition of the mold resin 62, and position P3 is the +X-side endposition of the mold resin 62.

That is, in the light emitting device 10 with the mold resin 62, theadhesion strength increases in portions on the +X side and the −X sideof the joint part 100, and, therefore, the peeling of the joint part 100is sufficiently suppressed by the mold resin 62. Note that the adhesionstrength from position P0 to position P1 is the strength of adhesionbetween the mold resin 62 and the coverlay 42 of the flexible wiringsubstrate 40. Furthermore, the adhesion strength from position P2 toposition P3 is the strength of adhesion between the mold resin 62 andthe substrate 22 of the light emitting panel 20.

FIG. 33 shows the average value of ten samples of ten light emittingdevices 10 in the average 90-degree peeling durability test. FIG. 34shows the average value of the adhesion strength test of ten lightemitting devices 10. Furthermore, forty light emitting devices 10 wereused to test the tensile reliability of the joint part. After that,twenty light emitting devices 10 were left for 500 hours in anenvironment in which the temperature was 85° C. and the humidity was85%, and another twenty light emitting devices 10 were left for 1000hours. After that, electricity was applied to the light emitting devices10. Then, the number of light emitting devices 10 in which none of thelight emitting elements 30 on the light emitting panel 20 failed tolight was counted. The results are shown in FIG. 33 .

The results of the joint-part tensile reliability test showed that nosamples of the light emitting devices 10A to 10D of examples 1 to 4demonstrated lighting defects even after 500 hours of operation in thehigh-temperature, high-humidity test, or even after 1000 hours ofoperation. In addition, for examples 1 to 4, the repeated-bendingreliability of the joint part was tested using forty light emittingdevices for each of light emitting devices 10A to 10D. The results areshown in FIG. 34 . No samples of light emitting devices 10A to 10D ofexamples 1 to 4 demonstrated lighting defects even after 500 hours ofoperation in the high-temperature, high-humidity test, or even after1000 hours of operation.

Comparative Examples 1 and 2

Light emitting devices 10 according to comparative examples 1 and 2 arelight emitting devices that are manufactured using composite sealingmaterials 63 with mold resins 62 that were 40-μm thick and 140-μm thick,respectively. Except for the thickness of the mold resins 62, theconfiguration and the manufacturing process were the same as those ofthe light emitting device 10A of example 1. With the light emittingdevices 10 according to comparative examples 1 and 2, in some samples,voids and infiltration of the infiltration solution were observed, andthe adhesion strength in the average 90-degree peeling durability testshowed low values compared to the light emitting devices 10A to 10D ofexamples 1 to 4. Similar to the light emitting device 10A according toexample 1, the tensile reliability of the joint part was tested, and therepeated-bending reliability of the joint part was tested. The resultsare shown in FIG. 33 and FIG. 34 . In both tests, there were samplesthat demonstrated lighting defects.

Comparative Example 3

The light emitting device 10 according to comparative example 3 is alight emitting device, in which the joint part 100 is molded using anepoxy adhesive for the mold resin 62, to make its thickness 80 μm,without using a protective tape 60. The configuration and themanufacturing process were the same as those of the light emittingdevice 10A of example 1, except that no protective tape 60 was used. Forthe light emitting device 10 of comparative example 3, thecross-sectional void observation test, the infiltration search test, theaverage 90-degree peeling durability test, the adhesion strength test,the joint-part tensile reliability test and the joint-part repeatedbending reliability test were conducted in the same procedures as withthe light emitting device 10A according to example 1. The results areshown in FIG. 27 , FIG. 33 , and FIG. 34 . In all tests, there weresamples that demonstrated lighting defects.

Comparative Example 4

The light emitting device 10 according to comparative example 4 is alight emitting device that is manufactured by winding only theprotective tape 60 around the joint part 100, without using a mold resin62. The configuration and the manufacturing process were the same asthose of the light emitting device 10A of example 1, except that no moldresin 62 was used. For the light emitting device 10 of comparativeexample 4, the cross-sectional void observation test, the infiltrationsearch test, the average 90-degree peeling durability test, the adhesionstrength test, the joint-part tensile reliability test and thejoint-part repeated bending reliability test were conducted in the sameprocedures as with the light emitting device 10A according to example 1.The results are shown in FIG. 27 , FIG. 33 , and FIG. 34 . All testsproduced results that indicated severe unreliability.

FIG. 41 is an image showing a cross-section of the light emitting device10 according to comparative example 1. This image corresponds to thecross-section shown in FIG. 20 . As shown in the photo of FIG. 41 , withthe light emitting device 10E, voids were observed at the locationsindicated by the arrows. The white parts in the photo are voids. Withthe light emitting device 10 according to comparative example 1, in bothof the cross-sectional void observation test and the infiltration searchtest, voids and infiltration of the penetration search solution wereclearly observed.

On the other hand, as shown in FIG. 27 , with the light emitting device10A according to example 1, which used a composite sealing material 63with a mold resin 62 that was 60-μm thick, no filling failure wasconfirmed with any of the five samples. Also, with the light emittingdevices 1013, 10C and 10D according to examples 2 to 4 that usedcomposite sealing materials 63 with mold resins 62 that were 80-μmthick, 100-μm thick and 120-μm thick, respectively, no filling failureof the mold resin 62 was confirmed in either of the cross-sectional voidobservation test and the infiltration search test.

FIG. 42 is an image showing a cross-section of the light emitting device10C according to example 3. This image corresponds to the cross-sectionshown in FIG. 20 . As shown in the photo of FIG. 42 , with the lightemitting device 10C, the mold resin 62 is filled between the protectivetape 60 and the substrate 22, without a gap.

When the light emitting device 10 according to comparative example 2 wasused, the mold resin 62 flew out from position P3 in FIG. 31 —that is,from an end of the composite sealing unit 61—onto the surface of thelight emitting panel 20, covered part of the light emitting panel 20,and, as a result of this, partially damaged the translucency andvisibility of the light emitting panel 20.

Example 5

With the light emitting device 10 according to example 5, an acrylicthermoplastic resin that was 80-μm thick was used for the mold resin 62for constituting the composite sealing material 63, and apolyamide-based film was used for the protective tape 60. The thicknessof the mold resin 62 was the same as in example 2. The configuration andthe manufacturing process were both the same as those of the lightemitting device 10A of example 1, except for the material and thethickness of the mold resin 62. Seventy light emitting devices 10according to example 5 were manufactured. Then, following the sameprocedures as with the light emitting devices 10A to 10D according toexamples 1 to 4, the above-described cross-sectional void observationtest and infiltration search test were conducted for five light emittingdevices 10 according to example 5, and, similarly, the above-describedaverage 90-degree peeling durability test and adhesion strength testwere conducted for ten light emitting devices 10E according to example5. Furthermore, using forty light emitting devices 10 according toexample 5, a joint-part repeated bending reliability test was conducted,in which one set of a tension operation and an extension operation wasperformed for 400 cycles and 1000 cycles.

Example 6

With the light emitting device 10 according to example 6, instead ofpolyimide, a 20-μm thick polyether ether ketone (PEEK) film was used forthe protective tape 60 of the composite sealing material 63. Athermosetting polyimide resin was used for the mold resin. Theconfiguration and the manufacturing process were both the same as thoseof the light emitting device 10A of example 1, except for the materialsof the protective tape 60 and the mold resin 62. Seventy light emittingdevices 10 according to example 6 were manufactured. Then, following thesame procedures as with the light emitting devices 10A to 10D accordingto examples 1 to 4, the above-described cross-sectional void observationtest and infiltration search test were conducted for five light emittingdevices 10 according to example 6, and, similarly, the above-describedaverage 90-degree peeling durability test and adhesion strength testwere conducted for ten light emitting devices 10 according to example 6.Furthermore, using forty light emitting devices 10 according to example6, a joint-part repeated bending reliability test was conducted, inwhich one set of a tension operation and an extension operation wasperformed for 400 cycles and 1000 cycles.

Examples 7 and 8, and Comparative Examples 5 and 6

Example 1 to 6 and comparative examples 1 to 4, which have beendescribed above, are designed so that a gap of 2 mm is formed between anend surface of the light emitting panel 20 and an end surface of theflexible wiring substrate 40. Unless a gap is designed between an endsurface of the light emitting panel 20 and an end surface of theflexible wiring substrate 40, the mold resin 62 cannot enter betweenthese end surfaces, and there is a possibility that voids are formed,both end surfaces get too close and bulge up, and peeling occurs in theconductor layer of the flexible wiring substrate 40, in the joint partwhere the anisotropic conductive film is used, and so forth. Inaddition, if the gap between an end surface of the light emitting panel20 and an end surface of the flexible wiring substrate 40 is too wide,the mold resin 62 may be filled unevenly, or the strength of adhesionmay be reduced. Therefore, from the perspective of environmentalreliability, an attempt was made to experimentally find out anappropriate distance between an end surface of the light emitting panel20 and an end surface of the flexible wiring substrate 40.

In example 7 and comparative example 5, the light emitting devices 10were assembled carefully so that the gap between an end surface of thelight emitting panel 20 and an end surface of the flexible wiring board40 was 1.3 mm and 0.8 mm, respectively. In addition, in example 8 andcomparative example 6, the light emitting deices 10 were assembledcarefully so that the gap between the end surface of the light emittingpanel 20 and the end surface of the flexible wiring board 40 was 4.5 mmand 5.2 mm, respectively. In this way, the light emitting devices 10according to examples 7 and 8 and comparative examples 5 and 6 weremanufactured. In terms of other aspects, including material selection,the manufacturing process and so forth, the light emitting devices 10were manufactured in completely the same manner as the light emittingdevice 10A according to example 1.

FIG. 27 shows values of gap dl between an end surface of the lightemitting panel 20 and an end surface of the flexible wiring board 40that were actually measured during the cross-sectional void observationof light emitting devices 10 according to examples 7 and 8 andcomparative examples 5 and 6, that had been assembled. As shown in FIG.27 , it is clear that the light emitting devices 10 according toexamples 7 and 8 and comparative examples 5 and 6 were manufactured asdesigned. With each sample, the cross-sectional void observation test,the infiltration search test, the average 90-degree peeling durabilitytest, the adhesion strength test, the joint-part tensile reliabilitytest, and the joint-part repeated bending reliability test wereconducted in the same procedures as in the case of the light emittingdevice 10A according to example 1. The results are shown in FIG. 27 ,FIG. 33 , and FIG. 34 . From these results, it was found out thatsufficiently reliable connection could not be achieved unless gap dlbetween an end surface of the light emitting panel 20 and an end surfaceof the flexible wiring board 40 was 1 mm or more and 5 mm or less.

Of the examples and comparative examples described above, correlationsamong the reliability test, the peeling durability and the adhesionstrength were examined, based on a regression analysis, with respect toexamples where not all samples lit after 500 hours of operation or 1000hours of operation in the high-temperature and high-humidity testfollowing the test of the tensile reliability of the joint part and/orthe test of the repeated-bending reliability of the joint part.

Determining coefficient R² of the polynomial regression curve betweenthe results of the tensile reliability test for the joint part and thepeeling durability was 0.711, while determining coefficient R² of thepolynomial regression curve between the results of the tensilereliability test for the joint part and the adhesion strength was 0.691.Therefore, it is possible to say that the results of the tensilereliability test for the joint part are more strongly correlated withthe peeling durability. To ensure the tensile reliability of the jointpart, the peeling durability needs to be at least 4 N/cm or more,preferably 6 N/cm or more, and more preferably 8 N/cm or more, evenunder the high-temperature and high-humidity environment, normallyrequired for automotive parts that need to operate for 1000 hours in anenvironment in which the temperature is 85° C. and the humidity is 85%.However, the data of example 5 is not included. The reason for thisarises from the material-specific problem that acrylic resins aresusceptible to degenerate at high temperature and high humidity.

Next, of the examples and comparative examples described above,correlations among the reliability test, the peeling durability and theadhesion strength were examined, based on a regression analysis, withrespect to examples where not all samples lit after 500 hours ofoperation or 1000 hours of operation in the high-temperature andhigh-humidity test following the test of the tensile reliability of thejoint part and/or the test of the repeated-bending reliability of thejoint part.

Determining coefficient R² of the polynomial regression curve betweenthe results of the repeated-bending reliability test for the joint partand the peeling durability was 0.847, while determining coefficient R²of the polynomial regression curve between the results of the tensilereliability test for the joint part and the adhesion strength was 0.864.Therefore, it is possible to say that the results of therepeated-bending reliability test for the joint part are more stronglycorrelated with the adhesion strength.

To ensure the repeated-bending reliability of the joint part, theadhesion strength needs to be at least 6 N/cm or more, preferably 8 N/cmor more, even under the high-temperature and high-humidity environment,normally required for automotive parts that need to operate for 1000hours in an environment in which the temperature is 85° C. and thehumidity is 85%. However, the data of example 7 is not included. Thereason for this arises from the material-specific problem that acrylicresins are susceptible to degenerate at high temperature and highhumidity.

The light emitting devices 10 according to the herein-containedembodiments are flexible. Consequently, as shown in FIG. 38 , forexample, a light emitting device 10 according to an embodiment can beused to decorate a showcase 500 or the like that displays goods and thelike over a curved glass 501. Even if the light emitting device 10 isarranged on the curved glass 501, it is possible to display goodsthrough the light emitting device 10. Consequently, it is possible toshow messages using the light emitting device 10, without damaging thedisplay of goods. By arranging a plurality of light emitting devices 10side by side, display to suit the size of the showcase 500 becomespossible. The light emitting device 10 can be used to provide variousdecorations and messengers as well as decorations for showcases and showwindows.

The light emitting devices 10 according to the herein-containedembodiments can be used for tail lamps for vehicles. By using a lightemitting device 10, which is translucent and flexible, as a lightsource, various visual effects can be produced. FIG. 39 is a diagram toshow, schematically, a cross-section of a resin casing in a horizontalplane, and its internal structure, with respect to a tail lamp 800 for avehicle 850. The light emitting device 10 is arranged along the innerwall surface of the resin casing of the tail lamp 800, and a mirror 801is arranged on the back surface of the light emitting device 10, so thatlight that is emitted from the light emitting device 10 toward themirror 801 is reflected by the mirror 801, and then passes through thelight emitting device 10, and is emitted to the outside. By this means,a unit that is configured as if having a light source apart from thelight emitting device 10 in the depth direction of the tail lamp 800 canbe formed.

The light emitting devices 10 according to the above-describedembodiments have assumed that the light emitting elements 30 arearranged on a straight line as shown in FIG. 4 . This is by no meanslimiting, and, for example, as shown in FIG. 40 , the light emittingelements 30 may be arranged in a matrix shape on a two-dimensionalplane.

Although embodiments of the present invention have been described above,the method of manufacturing light emitting devices 10 is disclosed indetail in US Patent Application Publication No. 2017/0250330(WO/2016/047134). As shown in FIG. 40 , a light emitting device in whichlight emitting elements are arranged in a matrix shape is disclosed indetail in Japanese Patent Application No. 2018-164963. Their contentsare incorporated herein by reference.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

The invention claimed is:
 1. A light emitting device comprising: a lightemitting panel comprising: a first substrate, which is flexible, aplurality of conductor patterns, which are formed on a surface of thefirst substrate, a plurality of light emitting elements, each of whichis connected to at least two of the conductor patterns, and a resinlayer, which holds the light emitting elements on the first substrate; awiring substrate comprising: an insulating base, and a circuit patternthat is formed on the insulating base and electrically connected with anexposed part of the conductor patterns that is exposed from an end partof the resin layer; and a mold resin, which covers part of the conductorpatterns and part of the circuit pattern, and which covers the end partof the resin layer and an end part of the insulating base.
 2. Thelight-emitting device according to claim 1, further comprising: aprotective tape, which is affixed around a joint part of the lightemitting panel and the wiring substrate.
 3. The light-emitting deviceaccording to claim 1, wherein the first substrate comprises at least oneof polyethylene terephthalate (PET), polyethylene naphthalate (PEN),polycarbonate (PC), polyethylene succinate (PES), cyclic olefin resin,acrylic resin or polyimide.
 4. The light-emitting device according toclaim 1, wherein the light emitting element comprises a pair ofelectrodes located at a first surface of the light emitting element, thepair of electrodes being connected to respective ones of the pluralityof conductor patterns.
 5. The light-emitting device according to claim1, wherein the conductor patterns and the circuit pattern are connectedusing an anisotropic conductive film.
 6. The light-emitting deviceaccording to claim 1, wherein the wiring substrate comprises aconnector.
 7. The light emitting device according to claim 1, whereinthe mold resin is filled between the end part of the resin layer and anend part of the wiring substrate.
 8. The light emitting device accordingto claim 1, further comprising a second substrate, which is arranged toface the first substrate with the plurality of light emitting elementslocated between the first substrate and the second substrate.
 9. Thelight-emitting device according to claim 8, wherein the second substratecomprises at least one of polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polycarbonate (PC), polyethylene succinate (PES),cyclic olefin resin, acrylic resin or polyimide.
 10. The light-emittingdevice according to claim 2, wherein the protective tape is made of amaterial that is heat resistant and insulative.
 11. The light-emittingdevice according to claim 8, wherein: the second substrate faces thesurface of the first substrate on which the conductor pattern is formed,and a thickness of the conductor pattern is not less than 0.05 μm andnot more than 2.0 μm.
 12. The light-emitting device according to claim8, wherein: the resin layer is an insulator that is formed between thefirst substrate and the second substrate, and a thickness of the moldresin is not less than 50 μm and not more than 100 μm.
 13. Thelight-emitting device according to claim 8, wherein the first substrateand the second substrate comprise at least one of polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC),polyethylene succinate (PES), cyclic olefin resin, acrylic resin orpolyimide.
 14. The light-emitting device according to claim 8, whereinthe first substrate and the second substrate have curved shapes so thatparts where the plurality of the light emitting elements are arrangedprotrude outward.
 15. The light-emitting device according to claim 8,wherein, in a top view, the first substrate and the second substrate arerectangular, the first substrate and the second substrate aretransparent to visible light, and a total luminous transmittance of thefirst substrate and the second substrate is not less than 5% and notmore than 95%.
 16. The light-emitting device according to claim 15,wherein the first substrate is a film-like member.
 17. Thelight-emitting device according to claim 1, wherein the first substratehas a total light transmittance of 5% or more and 95% or less.